The present invention relates to a spinal disc prosthesis to replace a damaged or degenerated spinal disc in a spinal column of a human.
U.S. Pat. Nos. 5,017,437 and 5,534,030 disclose typical spinal disc prostheses to replace a damaged or degenerated spinal disc in a spinal column of a human. The discs disclosed in these patents include a pair of rigid plates adhered to opposite surfaces of a body of elastomeric material.
The disc when in use is positioned between adjacent vertebrae. The disc is subject to forces which act in the spine including compression forces due to loads on the spine, tension forces due to bending of the spine, and torsional forces due to twisting of the spine. These forces can be applied simultaneously to the disc. These forces act to attempt to separate the rigid plates from the body of elastomeric material.
The present invention relates to a spinal disc prosthesis to replace a damaged spinal disc in a spinal column of a human. The spinal disc prosthesis includes a body of elastomeric material located between and bonded to upper and lower rigid plates. The body of elastomeric material includes a main portion and a peripheral portion extending around the main portion.
The upper and lower plates each have a curved convex plate surface extending around the respective outer perimeters and facing the peripheral portion of the body of elastomeric material. The peripheral portion of the body of elastomeric material has a first part which is bonded to the curved convex plate surfaces of the upper and lower plates and extends toward the main portion. The first part of the peripheral portion increases in thickness as the first part extends from the curved convex plate surfaces toward the main portion. The first part of the peripheral portion of the body of elastomeric material has a convexly curved outer surface which forms a part of the outer surface of the body of elastomeric material.